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Analytic initial conditions and verifying parameter estimation for black hole binaries

Klinger, Talya 2023. Analytic initial conditions and verifying parameter estimation for black hole binaries. MPhil Thesis, Cardiff University.
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The LIGO-Virgo Collaboration utilises nested sampling to infer the source properties of compact binaries, computing Bayesian evidences and posterior distributions. With poor sampling from the constrained prior, nested sampling algorithms may misbehave and fail to sample the posterior distribution faithfully. Fowlie et al. (2020) outlines a method of identifying pathologies such as plateaus in the parameter space, using likelihood insertion order statistics. We apply this method to nested sampling analyses of all events in the first and second gravitational wave transient catalogs. With a few exceptions that have negligible effect on the final posteriors, the data is consistent with uniform insertion order statistics and unbiased prior sampling. There is, however, weak evidence against uniformity at the catalog- level meta-test. With improvements to the LIGO-Virgo-Kagra detector network and future gravitational-wave interferometers planned, the demand for accurate and efficient numerical relativity codes becomes more pressing. Black hole binaries (BBHs) with very asymmetric mass ratios create a significant speed bottleneck, requiring a small grid spacing to resolve. In the moving-puncture formalism of numerical relativity, black holes are represented by trumpets, with an asymptotically flat exterior surrounding an infinitely long cylinder. While there is an analytic expression for the stationary trumpet spacetime, its behavior in a realistic BBH simulation scenario– i.e., a Lorentz boosted trumpet in 1+log slicing–is less well understood. We derive and sketch the numerical solution of a two-dimensional boundary value problem for the boosted 1+log trumpet coordinates. Such a solution could be subtracted from binary data to capture the strong field features of the low-mass partner, allowing for lower resolution and faster evolution.

Item Type: Thesis (MPhil)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Uncontrolled Keywords: numerical relativity, gravitational wave astronomy, nested sampling, trumpet coordinates
Funders: Self
Date of First Compliant Deposit: 13 June 2023
Last Modified: 06 Jan 2024 04:21

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